Stents are generally tubular shaped devices that function to hold open a segment of a blood vessel or other anatomical lumen and are useful in the treatment of atherosclerotic stenoses in blood vessels. Stents are particularly suitable for use in supporting and holding back a dissected arterial lining that can occlude the fluid passageway there through.
Stents are available in a variety of configurations, including self-expanding and mechanical expanding varieties, but regardless of the configuration, are typically delivered to the site of the atherosclerotic stenosis through the use of a catheter delivery device.
To accomplish precise placement of stents, various means are employed for identifying the position of the stent within a blood vessel. As the stents themselves are typically formed of a metal, metal alloy or polymeric material which is not readily visible using known techniques for viewing the stent such as fluoroscopy or MRI, such characteristics must be imparted to the stent structure. One method is to impart radiopacity to the stent structure such as by attachment of markers to the stent structure, or by making the entire stent from a radiopaque material, so that, through the use of fluoroscopy, the position of the stent within a blood vessel can be identified. Once the stent with its radiopaque markers has been implanted, identification of the stent position during subsequent checkups of the treated segment is easily accomplished because the markers remain visible under fluoroscopy. Another method is to provide stent materials which are visible using MRI.
Stents are most commonly formed of materials which have little radiopacity such as stainless steel or shape memory metal alloys such as NITINOL® which is a nickel-titanium shape memory alloy, for example. For one, making the entire stent out of a radiopaque material can be quite costly. Another disadvantage is that the stent may fluoresce too brightly which may actually make it more difficult for the physician to accurately position the stent, as well as to make follow up checks on the functioning of the stent more difficult.
There have been several methods employed for attaching radiopaque markers to a stent. One method has been to coat the deformable portions of the stent with radiopaque material. This can require a relatively thick coating in order to provide enough radiopaque material to be visible using fluoroscopy, and can also alter the mechanical performance of the stent.
Another method has been to insert radiopaque material into a hollow stent wire.
Other methods of attaching radiopaque markers have been employed such as that described in U.S. Pat. No. 6,334,871 in which radiopaque markers described therein as rivets are inserted into openings in the stent.
There remains a need in the art for improved stents as well as other improved intraluminal medical devices which are easily and readily visualized in the vasculature of a patient for accurate placement and for accurate future detection in the desired body lumen, and to improved methods of making the same.
All U.S. patents and applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.